How would I create an arch?
You can use an array + the simple deform modifier.


Start with a cube, this will be your "brick":

add an array modifier, make it as long as you want bricks. make them go up on the Z axis

add a simple deform modifier.
set the type to bend.
set the angle to 180
Add an empty at the origin of your object

Rotate it by 90 degrees on the Y axis.
Set it to the origin in the bend modifier
Move it away from your object to control the width of your arch, you may have to try multiple axis.

GIF